Usually, it would mean that the army took the land (forcefully if the owner resisted) after going through the formal process of issuing a "requisition order" or similar. So there is both formality and (potential) force involved, which is perhaps why dictionaries "seems to have both meanings".

A similar word is "commandeer" where there no formality involved. Here is an example:

- The police car would not start, so the police commandeered my car so that they could chase the thief.

In time of war, I suspect that the army would have commandeered the land from your unfortunate owner since there would have been no time for formality.